Field of the Invention
The present invention relates to a pen cap for a ball-point pen, and more particularly to a pen cap with pressure relief means which enables excessive air pressure to be released when the cap body of the pen cap is closed on the pen and, which prevents an ink leakage when completely closed on the pen.
When a pen cap is closed on a ball-point pen, inside air cannot escape out of the pen cap, therefore the pressure of air inside the pen cap is greatly increased when the pen cap is fully closed on the pen, causing ink to leak out of the pen. In order to eliminate this problem, there is provided a pen cap with pressure relief means. This structure of pen cap, as shown in FIG. 1, comprises a cap body 10 having an inner barrel 101 and an exhaust hole 102 at the center of the closed outer end of the inner barrel 101, a spring 20 mounted within the inner barrel 101, a socket 40 mounted within the inner barrel 101 and supported on the spring 20, and a rubber gasket 30 fastened to the socket 40 at one end. When the pen cap 10 is closed on the pen, excessive air pressure is released out of the pen cap through the exhaust hole 102. When the pen cap 10 and the pen are firmly fastened together, the writing tip of the pen is stopped at the rubber gasket 30 and retained inside the socket 40 in an air tight manner. This structure of pen cap eliminates an ink leakage. However, this structure of pen cap is expensive to manufacture, and complicated to assemble.